The present invention relates to an article of footwear including a midsole design and construction. More particularly, the invention relates to a midsole assembly having a key hole construction.
Traditionally, shoes and boots are fabricated by shaping the footwear over a last. A last is a three-dimensional shape of the inside cavity of a boot or shoe. The last may be mounted upside down for ease of manipulation and assembly of the components making up the footwear. The upper and sole are generally placed over the last in pieces or assemblies and secured together. A preassembled component upper consists of various layers of fabric and/or leather material sewn and/or glued together to form the upper or a portion of the upper shoe. Occasionally, the upper or sole are reinforced with rigid components, which have the general configuration of the finished product but have not yet been shaped to the final form of the footwear.
The rigidity and flexibility characteristics of the footwear are achieved by interposing the various layers of materials having suitable mechanical properties in specific regions of the footwear. In one typical assembly process, an insole is positioned on the top portion of the inverted last, which represents the inside bottom part of the article of footwear and the preassembled fabric component is then positioned over the last. The fabric components are stretched over the last and pushed over the insole to conform to the specific shape of the last and then nailed, tacked, and/or glued to the insole to maintain the desired shape. Often rigid plastic components are added to the sole construction to increase the strength and support of the footwear in specific areas. The footwear is usually completed with a midsole or cushioning and then an outsole nailed, tacked and/or glued to the assembly of components on the last.
Today, the sole design for modern athletic footwear for running, hiking and walking is characterized by a multi-layer construction comprising an outsole, midsole, and insole. The midsole is typically composed of a soft, foam material which provides cushioning properties to the shoe. However, a midsole formed from only a soft foam material is often ineffective for not only athletic shoes for running and other related sports, but also for hiking boots and other shoes used in an active lifestyle. Specifically, if the midsole is formed only of a soft foam material, the shoe can have excessive deformation which can lead to injuries. In addition, soft foam materials also impart instability that increases in proportion to midsole thickness. For this reason, footwear design often involves a balance of cushioning elements and stability elements.
In order to better understand the balancing of cushioning and stability in an athletic shoe, it is necessary to understand the general motion of the foot impacting the ground. First, the heel strikes the ground, followed by the ball of the foot. As the heel leaves the ground, the foot rolls forward so that the toes make contact, and finally the entire foot leaves the ground to begin another cycle. During the time that the foot is in contact with the ground, it typically rolls from the outside or lateral side to the inside or medial side, a process called pronation. Thus, normally, the outside of the heel strikes first with the toes on the inside of the foot leaving the ground last. While the foot is air borne and preparing for another cycle the opposite process, called supination, occurs. Although the inward roll of the foot in contact with the ground, although normal, pronation can be a potential source of foot and leg injury, particularly if it is excessive.
In order to help reduce injuries caused by pronation, soft foam materials were added to the midsole. However, as set forth above, the use of soft cushioning materials in the midsole of running shoes, while providing protection against impact forces, resulted in instability of the ankle, thereby contributing to the tendency for over-pronation and other athletic injuries.
In addition to the control of pronation, athletic footwear includes another type of foot motion requiring an article of footwear having stability. This type of motion is lateral, sideways or cutting movements. An athlete or someone involved in an active lifestyle may be required to perform a variety of motions including movement to the side, quickly executed direction changes, and stops and starts. While making such movements, if the midsole is not stable, the individual may suffer excessive inversion or eversion of the ankle joint, otherwise known as an ankle sprain.
Accordingly, stability as well as adequate cushioning properties are required in athletic shoes including walking and running shoes and hiking boots. Thus, there is a need for a midsole construction which prevents the midsole from excessively being deformed when contacting with the ground while providing adequate cushioning. It is therefore an object of the present invention to provide an article of footwear, in particular a sports shoe, where the article of footwear has an improved stability with cushioning properties.
In accordance with one aspect of the present invention, a midsole assembly for an article of footwear having a heel, a midsection and a forefoot, the midsole including a first member having a first hardness, the first member forming a continuous heel support, shank, and forefoot plate; a second member having a second hardness, the second member forming a continuous heel cushion and forefoot cushion; and wherein the first member is positioned beneath the second member in the heel, and positioned above the second member in the forefoot.
In accordance with another aspect of the present invention, a midsole assembly for an article of footwear having a heel, a midsection, and a forefoot, the midsole including a semi-rigid member, the semi-rigid member forming a heel support, a shank, and a forefoot plate; and a foam member, the foam member forming a cushion portion in the heel and forefoot, the semi-rigid member is positioned beneath the foam member in the heel and the midsection, and wherein the semi-rigid member is positioned above the foam member in the forefoot.
In accordance with a further aspect of the present invention, a midsole assembly for an article of footwear having a heel, a midsection, and a forefoot including a first member having a first hardness, the first member forming a heel support and forefoot plate; a second member having a second hardness, the second member forming a cushion in the heel and forefoot; and wherein the first member is positioned beneath the second member in the entire heel region and positioned above the second member in the entire forefoot region.
In accordance with another aspect of the present invention, an article of footwear including an upper for receiving a foot of a wearer; a midsole assembly, the midsole assembly including a first member, the first member forming a continuous heel support, shank and forefoot plate; and a second member, the second member forming a continuous heel cushion and forefoot cushion, wherein the first member is positioned beneath the second member in the heel, and positioned above the second member in the forefoot; and an outsole.
In accordance with another aspect of the present invention, an article of footwear including an upper for receiving a foot of a wearer; a midsole assembly, the midsole assembly including a semi-rigid member, the semi-rigid member forming a heel support, a shank and a forefoot plate; and a foam member, the foam member forming a cushion portion in the heel and forefoot, wherein the semi-rigid member is positioned beneath the foam member in the heel and the shank, and positioned above the foam member in the forefoot; and an outsole.
In accordance with a further aspect of the present invention, a method of assembling a midsole for an article of footwear including the steps of forming a first member having a heel support, a shank, and a forefoot support; forming a second member providing cushioning in the heel and forefoot, the second member having an opening in a mid portion of the second member for positioning the first member through the second member; inserting the first member through the opening in the second member, wherein the first member is positioned beneath the second member in the heel and middle of the midsole and positioned above the second member in the forefoot; and combining the first member and second member to form a midsole assembly.
In accordance with a further aspect of the present invention, a method of assembling a midsole for an article of footwear including the steps of forming a semi-rigid member having a heel support, a shank, and a forefoot support; forming a soft foam member providing cushioning in the heel and forefoot, the soft foam member having an opening in a mid portion of the soft foam member for positioning the semi-rigid member through the soft foam member; inserting the semi-rigid member through the opening in the soft foam, wherein the semi-rigid member is positioned beneath the soft foam member in the heel and middle of the midsole and positioned above the soft foam member in the forefoot; and combining the semi-rigid member and soft foam member to form a midsole assembly.
Still other objects, features, and attendant advantages of the present invention will become apparent to those skilled in the art from reading of the following detailed description of embodiments constructed in accordance therewith, taken in conjunction with the accompanying drawings.